Replacement type dual variable resistor



Jan. 15, 1957 K. w. YOUNGBECK 2,777,924

REPLACEMENT TYPE DUAL VARIABLE RESISTOR Filed D60. 24, 1953 INVENTOR. KARL. W. YOUNGBECK yflfhuwu ATTORNEY Fue. 4

United States Patent O REPLACEMENT TYPE DUAL VARIABLE RESISTOR Karl W. Youngbeck, Milwaukee, Wis., assignor to Globe- Union Inc., Milwaukee, Wis., a corporation of Delaware Application December 24, 1953, Serial No. 400,285

1 Claim. (Cl. 201-55) This invention relates to dual variable resistors of the replacement type.

In order to replace custom dual controls in radio and television receivers a jobber would have to carry in the neighborhood of 400 different custom units to have a complete line. This is very unwieldy and expensive.

It is an object of this invention, therefore, to provide a replacement type dual variable resistor which is easily and quickly made by the Serviceman to match the electrical characteristics of the custom control to be replaced by selecting separate controls, measuring and cutting off their shafts and making a dual unit by merely snapping such separate controls together.

A jobber needs only maintain in stock in the neighborhood of 50 different completed separate controls with one type of shaft and a like number of completed separate controls with another type of shaft in order to supply to the servicemen enough combinations of controls to enable him to make replacements for approximately 400 different custom dual units. The front section control employs a sleeve shaft and the rear section control uses a small shaft which mounts concentrically in the sleeve shaft. The electrical characteristics of each separate control are varied by using different resistances. However, the resistors and rotors are of well known design. The front control section has a mounting bushing of conventional design by which the assembled dual unit is secured to a panel or chassis. The rear control section has a mounting cap which fits over the housing of the front control section and is snapped in place by tooth and notch means cooperating between such cap and the housing of the front control section. After selecting each section to match the electrical characteristics of the replaced custom dual control, the Serviceman measures the length of the shafts of such custom control from the face of its mounting bushing and applies such measurements to the sleeve shaft of the front control and to the small shaft of the rear control. The small shaft has a visible groove on the surface thereof which in the assembled condition of the sections is in alinement with the face of the mounting bushing and this is used to apply the measurement from the custom unit. The shaft for the rear section has a standard flat which will permit a variety of sizes of knobs to fit thereon. The sleeve shaft of the front section has standard flats so that a knob designed to fit a slot can be fitted thereon. These flats have milled grooves in the surface thereof which act as guides to cut slots in such sleeve shaft so that it will accommodate knobs which are designed to fit on slotted shafts. When the shafts have been cut to length and the sleeve shaft slotted, if necessary, the small shaft is fitted into the sleeve shaft and the sections snapped together to make the unit.

The characteristics and applications of this invention may be best understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Fig. l is a view in side elevation, with parts broken away ice and shown in section, of a replacement type dual variable resistor embodying the present invention;

Fig. 2 is an isometric exploded view of the rear section mounting cap and bushing forming a part of this invention;

Fig. 3 is an enlarged sectional view taken on the line 33 of Fig. 1; and

Fig. 4 is an enlarged sectional view taken on the lin 4-4 of Fig. l.

In the embodiment of the invention shown in the drawing the replacement type dual variable resistor has a front (to the left) control section 10 and a rear control section 12 which, when joined as shown in Fig. 1, make a dual unit which may be mounted to a panel so that each unit is separately operated by its own shaft. Each section has a resistance over which a rotor moves. By varying the value of the resistance a large range of sections may be obtained from which a great number of combinations may be made. The mechanical construction of each control section is identical and well known to those skilled in this art except for the mounting cap of the rear section and the external part of the operating shafts.

Each section has an insulating'base 14 on which are mounted terminal 16. Each has a cover with annular side walls 18 and flat rear wall 20. The latter has a central opening 22 therein to provide operating access to the control shaft from the rear. A head 24 is formed in the side wall 18 which is used in properly angularly relating the front and rear sections and any switch which might be added to the rear section. The side wall 18 also has opposite related teeth 26 which engage with notches in the manner hereinafter described to connect the sections with a snap action. Dimples 28 formed in the rear wall 20 are used to slightly deflect such wall when the sections are snapped together and provide resilient bias to hold the snap lock tight.

The front section 10 has a threaded mounting bushing 30 to which the cover 18 is secured by tabs 32. A sleeve shaft 34 is rotatably mounted in the bushing 30 and connected to the rotor by peening over end lugs 36. It is preferable to provide the sleeve shaft with a counterbore 38 to make the lugs 36 thinner and easier to bend without breaking. That portion of the shaft extending outwardly of the bushing 30 has a pair of opposed flats 40 (see Fig. 3). These flats will permit various sized knobs designed to fit on flats to be mounted on the sleeve shaft 34. In the face of each of these flats are spaced guide grooves 42. These grooves assist in cutting a slot in one or both of the flats 40, whenever it is necessary to mount a knob on the sleeve shaft 34 which is designed to fit on a slotted shaft. The length of the sleeve shaft 34 is long enough to cover all custom units which this replacement unit is designed to replace. When the custom unit is removed both its shafts are measured from the face of its mounting bush- 7 ing. The sleeve shaft measurement may be applied to sleeve shaft 34 before the rear section is assembled and the sleeve shaft 34 cut. The sleeve shaft 34 is held in proper position within the bushing 30 by a C-ring 44 which fits in an annular groove in the outer surface of the shaft. The front section when assembled with its sleeve shaft 34 constitutes a complete separate and independently variable resistance. it is possible to make in the neighborhood of 50 front sections which vary only in their electrical ranges.

The rear control section 12 has an intermediate mounting cap 46 with an annular wall 48 which slidably fits over the side wall 13 of the front control section. The annular wall 48 is provided with a channel 52 which fits over the head 24 to angularly locate the front and rear sections. Notches 54 in the annular wall 48 receive the teeth 26 on the front section and lock the mounting cap 46 in place.

. a3 Laterally deformed lips 56 on the periphery of the wall 48 permit the insertion under the wall of a small screw driver or other like instrumentality to pry the edges of the notch'es 54 out of contactwith the teeth -2d to disassemble the front and rear sections. The end "wallfiii 'has a central 'op'ening 58 provided wvi th notches'fi fl. bashing-W50 is fitted in such opening andstaked insuch notchesWith its rear end projecting beyond the end wall 5t? into an open- ;ing 62. inthe b'ase plate 14 to centralize such". plate and the mounting cap 46. As is most clearly shown inFi g. 2,

the end Wall50'has a pair of diametrically arranged rearwardly projecting pads 6.4 which provide seats for the base plate 14. A plurality ofirectzmgular openings seam ithe periphery of-such pads permit the tabs 32 to :enter intoithe si'de of thecap 46 and ibehent-over ondhe inner .facevof :the pads 64 softhat'theimounting' capfrnay be sect .to the-rear' sectionw12. .'A' srnall reartseetion shaft' 63 is rotatably carri'e'd in'the bushing 60 and connected in custornarymanner tothe rotatable part'of' the rear section. This sha'ft has a flat inner-iencl' 'iti which is'in axial *aline m'ent withthe central opening 22. PT his flat end may be elv held connected withthe coupler ofa line control switch which can b'eirnounted 'on the rear-section. Thershaft'e ris held inf'p'la'ce by a- C r'ing 72fitting in a groovetin' such shaft and bearing against lthe"bus'hing 60. The extended for- The requiredlength of the inner shaft 68 is: measured from an annular notch 76 solocatedl longitudinally on such shaft as tobe inalinement'with 'theface of the 'mounting bushing 30"whent-he rear sectionlZ is properly assembled to the front section.

When both the sleeve' shaft 34 of therfrontsection and the small shaft! 68 of therear section 12 have been cut to length to match 'the: length of the'shafts of the custom'unit, and the sleeve shaft 34'slotted' if necessary,

'the rear section 12 is assembled to the front sectionvby arm-924.

inserting the shaft 68 through the rear opening 22 into the sleeve shaft 34. With the channel 52. alined with the head 24 the rear section 12 is pressed forwardly on the front section 10 until the teeth 26 snap into the notches 54. The flat rear wall 20 of the front section will be slightly depressed by the engagement-between the dimples 28 and the forward face of the bushing 60. This will create a resilient bias trot apply. pressure" between" the =Jtee'th' 26. and

the notches 54. and hold thesectionsecurely in place witheut.' re1ative movement. 'f'lo'disconnectlthe rearse'ction from the front section a screwdriver or a like instrument is inserted under the lip 56 to raise the edge of the notch 54 out of engagement with'thetooth-Zfi.

In the neighborhoodloffront-and 50 rear sections can be made each of which vary in its electrical characteristics but are of the same physical dimensions and mechanical construction. Any one of the rear sections can be fitted on any one of the front sections'in the manner just described to make in excess of the-nnmbenofacombiriations 'required:for replacements. "The :servicemanican therefore make a' wi'de variety ofcombinations ofreplacementtype dual variable resistors to replacewustom-units made to 'manufacturersspecifications.

What' I cl'aim'and desire tosecurexbythispatent is:

A: multiple unit control'of the: replacement type, .com-

prising a first unithaving a mounting face forengagement with 'a 'panel and a sleeve- 'shaft rotatably mountedtherein sandtextendingoutwardlynfsaid':mounting face; :and asecond unit adapted to be snap-fitted ontolsaid first unitand having a small shaft extending throughsaidsleeve shaft and projecting outwardly thereofythe outwardly projecting portion 'of said 'sle'eveshafthaving a-pair of opposed fl'ats with spaced grooves cut' in from the faces of said flats and extending longitudinally'thereof; the grooves in one-i fiat being alinedv withthengrooves-ini theziotherrafiat so that said sleeve shaft' may lye-conveniently cuttoprovide a slotted end.

References Cited in the file of this patent UNITED STATES PATENTS 2,120,651 Schellenger dune" 14; I938 "240 1,037 Arvin May"28,-1 946 2,'484,"667 Arisman etal Oct. 11, 1949 2506;491

'Bois Blanc May 2, 1950 

